Heat exchanger arrangement and method for the operation of same

ABSTRACT

A heat exchanger arrangement is presented having at least one heat exchanger module ( 2 ), which includes a plurality of microchannel heat transfer elements ( 6.1, 6.2 ) and a plurality of heat exchange ribs ( 7.1, 7.2 ) which are connected to the microchannel heat transfer elements in a thermally conductive manner and which form air channels, and having a ventilation apparatus to generate an airflow ( 12 ′) in the air channels. The heat exchanger arrangement additionally includes a wetting apparatus to wet the microchannel transfer elements and/or the heat exchange ribs with liquid ( 10 ′). The heat exchanger arrangement is furthermore characterized in that the heat exchanger module or modules is/are arranged at an angle (α) with respect to the vertical.

The invention relates to a heat exchanger arrangement in accordance with the preamble of claim 1 and to a method for the operation of same in accordance with the preamble of claim 13.

Heat exchangers are used in a variety of technical applications for example in refrigeration systems and refrigeration apparatus for cooling rooms or domestic refrigerators, in heating systems and air conditioning systems for buildings or means of transportation such as automobiles, buses, ships and aircraft or as coolers in power stations, combustion engines, computers or other heat producing devices. In practical use, the heat exchangers are frequently connected to a circuit which contains a heat transfer medium such as a coolant, with the heat exchanger being able to absorb heat directly, i.e. without any phase conversion from the liquid or gaseous heat transfer medium, or being able to output it to the same or with it also being able to act as a condenser or as an evaporator for the heat transfer medium.

A widespread embodiment is the finned heat exchanger which is known, for example, from domestic refrigerators. In the simplest case, a finned heat exchanger is made up of a pipe for the conducting of a heat transfer medium and of a plurality of fins which are connected to the pipe and are in communication with a second medium in operation. This design is particularly expedient when the second medium is gaseous and consists, for example, of ambient air since it has a comparatively low heat transfer coefficient which can be compensated by a correspondingly large surface of the fins. The finned heat exchanger can naturally also include a plurality of pipes for more than one heat transfer medium or the pipes can be connected to one another in parallel and/or in series as required.

The efficiency is essentially determined by the temperature difference between the fins, on the one hand, and the pipe or pipes, on the other hand. The temperature difference is the smaller, i.e. the heat transfer the more effective, the greater the conductivity and the thickness of the fins and the smaller the mutual spacing of the pipes. It is thus advantageous with respect to the efficiency if a plurality of pipes are used. A plurality of pipes, however, also means higher material and processing costs so that a higher efficiency is normally associated with higher costs.

So-called microchannel heat transfer elements have therefore been used in heat exchangers for some years. They can, for example, be made as an extruded section which is manufactured from a material having good thermal conductivity, such as aluminum. The microchannel heat transfer elements, i.e. the extruded sections in the present case, include a plurality of channels having a diameter of typically 1 mm for the heat transfer medium. Other diameters are naturally also possible which can be, for example, in the range from 0.5 mm to 3 mm or 0.5 mm to 2 mm.

A condensation plant for use in a cooling system is described in the document EP 1 557 622 A2 to condense refrigerant evaporated for refrigerating purposes. The condensation plant described there includes a plurality of microchannel cooling coils which are each made as heat exchanger modules and one or more fans to generate an airflow through the heat exchanger modules. Each heat exchanger module includes a plurality of microchannel heat transfer elements, which are made as flat pipes and which are arranged parallel to and spaced apart from one other, as well as cooling ribs which are arranged between the flat pipes and are connected to same. The cooling ribs each form a zig-zag pattern between two adjacent pipes. The heat exchanger modules furthermore each include an inlet manifold and an outlet manifold which are connected to the microchannel heat transfer elements of the respective heat exchanger module. The condensation plant described in EP 1 557 622 A2 admittedly actually does have a compact design, but the base surface required for the installation of the plant is still considerable.

The object of the present invention is to provide a heat exchanger arrangement which allows the base surface required for the installation or the material effort or the energy effort for the ventilation to be reduced with respect to the prior art described above. A further object is to provide a method for a comparatively economic operation of the heat exchanger arrangement.

This object is satisfied in accordance with the invention by the heat exchanger arrangement defined in claim 1 and by the method defined in claim 13.

The heat exchanger arrangement in accordance with the invention is equipped with at least one heat exchanger module, which includes a plurality of microchannel heat transfer elements and a plurality of heat exchange ribs which are connected to the microchannel heat transfer elements in a thermally conductive manner and which form air channels, and with at least one ventilation apparatus to generate an airflow in the air channels. The heat exchanger arrangement additionally includes a wetting apparatus to wet the microchannel heat transfer elements and/or the heat exchange ribs with liquid, for example with water, and is furthermore characterized in that the heat exchanger module or modules is/are arranged at an angle with respect to the vertical.

The angle is advantageously determined in that the gravity and/or the inertia forces which act on drops of the liquid on or in a heat exchanger module in operation are in balance with the buoyancy forces of the airflow.

In an advantageous embodiment, the angle with respect to the vertical is between 10° and 40° or between 15° and 30°. In a further advantageous embodiment variant, the heat exchanger module or modules are each arranged horizontally.

In an advantageous embodiment, the microchannel heat transfer elements have a longitudinal direction and are each arranged at an angle to the vertical in the longitudinal direction. The microchannel heat transfer elements can in this respect be arranged at the same angle to the vertical as the respective heat exchanger module in which they are contained. On a case by case basis, the microchannel heat transfer elements can be arranged horizontally in the longitudinal direction.

In a further advantageous embodiment, the heat exchanger modules have a lower side and an upper side, in particular based on the arrangement at an angle to the vertical, with the ventilation apparatus being configured to generate an airflow from the lower side to the upper side in the air channels and with the wetting apparatus being configured to wet the microchannel heat transfer elements and/or the heat exchange ribs from the upper side or the lower side. The wetting apparatus is advantageously configured to wet the microchannel heat transfer elements and/or the heat exchange ribs both from the lower side and from the upper side.

In addition, the ventilation apparatus can be configured to generate an airflow from the upper side to the lower side in the air channels and the wetting apparatus can be configured to wet the microchannel heat transfer elements and/or the heat exchange ribs from the upper side.

In a further advantageous embodiment, openings and/or louvers are formed in the heat exchange ribs. In an advantageous embodiment variant, the openings or louvers are made as flow channels which, for example, have an attack angle with respect to the direction of the airflow or which have side walls, for example, with the side walls being able to be made to project with respect to the respective heat exchange rib and/or being able to have an attack angle with respect to the direction of the airflow. Thanks to the louvers or openings, in particular when they are made up of a plurality of small and/or narrow openings, the wetting liquid amount in the air channels can be increased.

Independently of the above-mentioned embodiments and embodiment variants, the angle (α) is advantageously adapted for a maximum cooling capacity with a given installation area of the heat exchanger arrangement and/or with a given total area of the heat exchanger modules.

In a further advantageous embodiment, the heat exchanger arrangement additionally optionally includes a humidification device arranged at the inlet side in the airflow for the cooling of the air and/or includes a drop catcher arranged at the outlet side in the airflow.

In the method in accordance with the invention for the operation of a heat exchanger arrangement in accordance with one or more of the above-described embodiments and embodiment variants, the quantity of the liquid supplied for the purpose of wetting the microchannel heat transfer elements and/or the heat exchange ribs and the speed of the airflow are regulated so that no drops or at most a fixed amount of drops of liquid present on or in a heat exchange module is/are taken along by the airflow.

In an advantageous embodiment variant of the method, the quantity of the liquid supplied for the purpose of wetting the microchannel heat transfer elements and/or the heat exchange ribs and the speed of the airflow are regulated such that the gravity and/or the inertia forces which act on drops of the liquid on or in a heat exchanger module are in balance with the buoyancy forces of the airflow.

The heat exchanger arrangement in accordance with the invention and the method in accordance with the invention have the advantage that, thanks to the wetting, the cooling capacity can be increased with respect to the initially described prior art with a given total area of the heat exchanger modules and a given speed of the airflow. On the other hand, the total area of the heat exchanger modules and/or the speed of the airflow can be reduced for a preset cooling capacity so that the efficiency of the heat exchanger arrangement is increased accordingly. Thanks to the circumstance that no drops or at most a fixed quantity of drops of liquid present on or in a heat exchanger module is/are taken along by the airflow, the energy expenditure for the generation of the airflow can be minimized. In addition, thanks to the openings or louvers formed in the heat exchange ribs, the wetting liquid amount and thus the cooling capacity at a given size of the heat exchanger arrangement can be increased or the material effort can be minimized with a preset cooling capacity.

The above description of embodiments and embodiment variants only serves as an example. Further advantageous embodiments can be seen from the dependent claims and from the drawing. Furthermore, individual features from the embodiments and variants described or shown can also be combined with one another within the framework of the present invention to form new embodiments.

The invention will be explained in more detail in the following with reference to the embodiments and to the drawing. There are shown:

FIG. 1 a schematic representation of an embodiment of a heat exchanger arrangement in accordance with the present invention;

FIG. 2 a schematic representation of an embodiment of a heat exchanger module for use in a heat exchanger arrangement in accordance with the present invention;

FIGS. 3A-3E embodiment variants for the direction of the airflow and the direction of the wetting in a heat exchanger arrangement in accordance with the present invention;

FIGS. 4A, 4B two embodiment variants for the arrangement of the microchannel heat transfer elements in a heat exchanger arrangement in accordance with the present invention;

FIG. 5A an embodiment for the configuration of the heat exchange ribs in a heat exchanger arrangement in accordance with the present invention; and

FIG. 5B a section through a heat exchange rib of the embodiment in accordance with FIG. 5A.

FIG. 1 shows a schematic representation of an embodiment of a heat exchanger arrangement in accordance with the present invention. The heat exchanger arrangement 1 is equipped with at least one heat exchanger module 2.1, 2.2, which includes a plurality of microchannel heat transfer elements and a plurality of heat exchange ribs which are connected to the microchannel heat transfer elements in a thermally conductive manner and which form air channels, and with at least one ventilation apparatus 4 to generate an airflow in the air channels. The heat exchanger arrangement 1 additionally includes a wetting apparatus 5 which can, for example, include one or more spray heads 5.1-5.4 to wet the microchannel heat transfer elements and/or the heat exchange ribs with liquid 10, for example with water, and is furthermore characterized in that the heat exchanger module or modules 2.1, 2.2 is/are arranged at an angle with respect to the vertical.

The wetting apparatus 5 can be arranged, for example, such that the heat exchanger modules 2.1, 2.2 are wetted from the interior of the heat exchanger arrangement, for example by means of spray heads 5.1, 5.2 and/or from the outside, for example by means of spray heads 5.3, 5.4, and/or the wetting apparatus can include a liquid distribution system 5.5, 5.6 which is integrated into the respective heat exchanger module 2.1, 2.2 and which is equipped, as shown in document DE 198 04 636 A1, for example, with outlet openings which are arranged in or at the respective heat exchanger module.

The angle is advantageously determined in that the gravity and/or the inertia forces which act on drops of the liquid on or in a heat exchanger module in operation are in balance with the buoyancy forces of the airflow. In an advantageous embodiment, the angle with respect to the vertical is between 10° and 40° or between 15° and 30°. In a further advantageous embodiment variant, the heat exchanger module or modules are each arranged horizontally. The size and number of the heat exchanger modules 2.1, 2.2 can be fixed in accordance with the required cooling capacity.

FIG. 2 shows a schematic representation of an embodiment of a heat exchanger module 2 for use in a heat exchanger arrangement in accordance with the present invention. The heat exchanger module shown includes a plurality of microchannel heat transfer elements 6.1, 6.2 which can, for example, be made as flat pipes and which are usually arranged parallel to and spaced apart from one another as well as a plurality of heat exchange ribs 7.1, 7.2 which are arranged between the microchannel heat transfer elements and are connected to the same in a thermally conductive manner, for example by means of a solder connection. The heat exchange ribs 7.1, 7.2 form air channels which extend perpendicular to the plane of the diagram in the heat exchanger module shown in FIG. 2. The heat exchanger ribs are typically made from a folded strip of sheet metal which can have a zig-zag pattern, for example.

The microchannel heat transfer elements 6.1, 6.2 can, for example, be made as an extruded section which is manufactured from a material having good thermal conductivity such as aluminum or an aluminum alloy. The microchannel heat transfer elements, i.e. the extruded sections in the present case, include a plurality of channels having a diameter of typically 1 mm for the heat transfer medium 3. Other diameters are naturally also possible which can be, for example, in the range from 0.5 mm to 3 mm or 0.5 mm to 2 mm.

If required, the heat exchanger module 2 can have an inlet manifold and an outlet manifold 8, 9, which are connected to the microchannel heat transfer elements 6.1, 6.2 in a liquid conductive manner, as well as an inlet 8 a and an outlet 9 a.

The individual parts of the heat exchanger module such as microchannel heat transfer elements 6.1, 6.2, heat exchange ribs 7.1, 7.2, inlet and outlet manifolds 8, 9 and inlet and outlet 8 a, 9 a can be made wholly or partly from aluminum or from an aluminum alloy and the assembled parts can be completely soldered in a soldering furnace.

FIGS. 3A-3E show embodiment variants for the direction of the airflow and the direction of the wetting in a heat exchanger arrangement in accordance with the present invention. In FIGS. 3A to 3E, the heat exchanger modules 2 are each arranged at an angle with respect to the vertical. In FIGS. 3A and 3E, the angle shown is <90°, whereas it amounts to 90° in the FIGS. 3B, 3C and 3D, i.e. the heat exchanger modules are arranged horizontally in FIGS. 3B, 3C and 3D. The heat exchanger modules 2 have a lower side and an upper side due to the arrangement at an angle to the vertical. In an advantageous embodiment, the ventilation apparatus is configured to generate an airflow from the lower side to the upper side in the air channels of the heat exchanger module 2 and the wetting apparatus is configured to wet the microchannel heat transfer elements and/or the heat exchange ribs of the heat exchanger modules from the upper side, as shown in FIG. 3D. This embodiment allows a high degree of wetting at low air speeds. It is, however, also possible to wet the microchannel heat transfer elements and/or the heat exchange ribs of the heat exchanger module from the lower side, as shown in FIGS. 3A and 3B. In the embodiment shown in FIG. 3A, the cooling capacity maximum is at an angle α of 10° to 40°. The embodiment shown in FIG. 3B with a horizontally arranged heat exchanger module requires a comparatively high air speed, with a power regulation only being possible with limitations by varying the air speed. The wetting apparatus is advantageously configured to wet the microchannel heat transfer elements and/or the heat exchange ribs both from the lower side and from the upper side, as shown in FIG. 3E. This embodiment allows a high degree of wetting with a low air quantity.

In addition, as shown in FIG. 3C, the ventilation apparatus can be configured to generate an airflow from the upper side to the lower side in the air channels and the wetting apparatus can be configured to wet the microchannel heat transfer elements and/or the heat exchange ribs from the upper side. In this embodiment, the excess water exiting on the lower side can be captured by baffles and recirculated.

Independently of the direction of the airflow and of the direction of the wetting, the cooling capacity can be regulated by varying the air speed or the liquid quantity for the wetting. In some embodiments, such as with an airflow from below and a wetting from above, the range in which the cooling capacity can be regulated by varying the air speed can be limited.

In the embodiment variants for the arrangement of the microchannel heat transfer elements in a heat exchanger arrangement in accordance with the present invention shown in FIGS. 4A and 4B, the heat exchanger modules 2 are each arranged at an angle α, α′ to the vertical which can, as shown there, be <90°. This angle can be of different magnitude for the optimization of the cooling object in dependence on the orientation of the microchannel heat transfer elements shown in FIGS. 4A and 4B. The heat exchanger modules shown each include a plurality of microchannel heat transfer elements 6.1, 6.2, which are usually arranged parallel to and spaced apart from one another, as well as a plurality of heat exchange ribs 7.1, 7.2, which are arranged between the microchannel heat transfer elements, are connected to same in a thermally conductive manner and form the air channels. The heat exchange ribs are typically made from a folded or bent sheet metal strip which can, for example, be soldered to the microchannel heat transfer elements in a soldering furnace.

In an advantageous embodiment, the microchannel heat transfer elements 6.1, 6.2 have a longitudinal direction and are each arranged at an angle to the vertical in the longitudinal direction. The microchannel heat transfer elements can in this respect, as shown in FIG. 4B, be arranged at the same angle α to the vertical as the respective heat exchange module 2 in which they are included, but can also be arranged at a further optimized angle α′ or the microchannel heat transfer elements can be arranged horizontally in the longitudinal direction, as shown in FIG. 4A. The running off of the wetting liquid can be facilitated by louvers which are formed in the heat exchange ribs 7.1. 7.2 with microchannel heat transfer elements not arranged horizontally in the longitudinal direction. In contrast, a larger angle α tends to result with microchannel heat exchange elements 6.1, 6.2 arranged horizontally in the longitudinal direction.

FIG. 5A shows an embodiment for the design of the heat exchange ribs in a heat exchanger arrangement in accordance with the present invention. The individual heat exchange ribs 7′ 7″ can be manufactured, for example, as shown in FIG. 5A, from a folded or bent sheet metal strip 7. In an advantageous embodiment, openings and/or louvers 11.1 are formed in the heat exchange ribs. Thank to the louvers or openings, in particular when they are made from a plurality of small and/or narrow openings, the wetting liquid quantity in the air channels can be increased and the propagation of a liquid film can be promoted in dependence on the arrangement. FIG. 5B shows a section through the embodiment in accordance with FIG. 5A. As shown in section, a plurality of louvers 11.1, 11.2 can be arranged next to one another or behind one another in the direction of the airflow 12. A possible wetting direction 10 is additionally drawn in FIG. 5B. All the directions of the airflow and wetting explained within the framework of the description of FIGS. 3A to 3E are naturally possible.

Independently of the above-mentioned embodiments and embodiment variants, the angle (α) is advantageously adapted for a maximum cooling capacity with a given installation area of the heat exchanger arrangement and/or with a given total area of the heat exchanger modules.

In a further advantageous embodiment, the heat exchanger arrangement additionally optionally includes a humidification device arranged at the inlet side in the airflow for the cooling of the air and/or includes a drop catcher arranged at the outlet side in the airflow.

The method in accordance with the invention for the operation of a heat exchanger arrangement in accordance with one or more of the embodiments and embodiment variants described above will be described with reference to FIGS. 1 and 2 in the following. In this method, the quantity of the liquid 10 which is supplied for the purpose of wetting the microchannel heat transfer elements 6.1, 6.2 and/or the heat exchange ribs 7.1, 7.2 and the speed of the airflow are regulated such that no drops or at most a fixed quantity of drops of liquid present on or in a heat exchanger module 2 is/are taken along by the airflow.

In an advantageous embodiment variant of the method, the quantity of the liquid 10 supplied for the purpose of wetting the microchannel heat transfer elements 6.1, 6.2 and/or the heat exchange ribs 7.1, 72 and the speed of the airflow are regulated such that the gravity and/or the inertia forces which act on drops of the liquid on or in a heat exchanger module 12 are in balance with the buoyancy forces of the airflow.

Thanks to the wetting with liquid, the performance capability of a heat exchanger arrangement with microchannel heat transfer elements and folded heat exchange ribs can be noticeably increased. In this respect, the cooling capacity increases by the evaporation heat of the evaporating liquid released per time unit, with the evaporation rate and thus the cooling capacity being able to be regulated via the degree of wetting and the air speed. 

1. A heat exchanger arrangement (1) having at least one heat exchanger module (2.1, 2.2), which includes a plurality of microchannel heat transfer elements (6.1, 6.2) and a plurality of heat exchange ribs (7, 7′, 7″, 7.1, 7.2) which are connected to the microchannel heat transfer elements in a thermally conductive manner and which form air channels, and having at least one ventilation apparatus (4) to generate an airflow (12, 12′, 12″) in the air channels, characterized in that the heat exchanger arrangement additionally includes a wetting apparatus (5) to wet the microchannel heat transfer elements and/or the heat exchange ribs with liquid (10, 10′, 10″); and in that the heat exchanger module or modules (2, 2.1, 2.2) is/are arranged at an angle (α) with respect to the vertical.
 2. A heat exchanger arrangement in accordance with claim 1, wherein the angle (α) is determined in that the gravity and/or the inertia forces which act on drops of the liquid (10, 10′, 10″) on or in a heat exchanger module (2, 2.1, 2.2) in operation are in balance with the buoyancy forces of the airflow (12, 12′, 12″).
 3. A heat exchanger arrangement in accordance with claim 1, wherein the angle (α) with respect to the vertical is between 10° and 40°, in particular between 15° and 30°.
 4. A heat exchanger arrangement in accordance with claim 1, wherein the heat exchanger module or modules (2, 2.1, 2.2) is/are each arranged horizontally.
 5. A heat exchanger arrangement in accordance with claim 1, wherein the microchannel heat transfer elements (6.1, 6.2) have a longitudinal direction and are each arranged at an angle to the vertical in the longitudinal direction; and wherein the microchannel heat transfer elements (6.1, 6.2) are in particular arranged at the same angle (α) to the vertical as the respective heat exchanger module (2, 2.1, 2.2) in which they are included.
 6. A heat exchanger arrangement in accordance with claim 1, wherein the microchannel heat transfer elements (6.1, 6.2) have a longitudinal direction and are arranged horizontally in the longitudinal direction.
 7. A heat exchanger arrangement in accordance with claim 1, wherein the heat exchanger modules (2, 2.1, 2.2) have a lower side and an upper side; and wherein the ventilation apparatus (4) is configured to generate an airflow (12, 12′, 12) from the lower side to the upper side in the air channels; and the wetting apparatus (5) is configured to wet the microchannel heat transfer elements (6.2, 6.2) and/or the heat exchange ribs (7, 7′, 7″, 7.1, 7.2) from the upper side or from the lower side.
 8. A heat exchanger arrangement in accordance with claim 7, wherein the wetting apparatus is configured to wet the microchannel heat transfer elements (6.1, 6.2) and/or the heat exchange ribs (7, 7′, 7″, 7.1, 7.2) both from the lower side and from the upper side.
 9. A heat exchanger arrangement in accordance with claim 1, wherein the heat exchanger modules (2, 2.1, 2.2) have a lower side and an upper side; and wherein the ventilation apparatus (4) is configured to generate an airflow (12, 12′, 12) from the lower side to the upper side in the air channels; and the wetting apparatus (5) is configured to wet the microchannel heat transfer elements (6.2, 6.2) and/or the heat exchange ribs (7, 7′, 7″, 7.1, 7.2) from the upper side.
 10. A heat exchanger arrangement in accordance with claim 1, wherein openings and/or louvers (11.1, 11.2) are formed in the heat exchange ribs (7, 7′, 7″, 7.1, 7.2).
 11. A heat exchanger arrangement in accordance with claim 1, wherein the angle (α) is adapted for a maximum cooling capacity with a given installation area of the heat exchanger arrangement (1) and/or with a given total area of the heat exchanger modules (2.1, 2.2).
 12. A heat exchanger arrangement in accordance with claim 1 additionally including a wetting device arranged at the inlet side in the airflow for the cooling of the air and/or including a drop catcher arranged at the outlet side in the airflow.
 13. A method for operation of a heat exchanger arrangement in accordance with claim 1, characterized in that the quantity of the liquid (10, 10′, 10″) which is supplied for the purpose of wetting the microchannel heat transfer elements (6.1, 6.2) and/or the heat exchange ribs (7, 7′, 7″, 7.1, 7.2) and the speed of the airflow (12, 12′, 12″) are regulated such that no drops or at most a fixed quantity of drops of the liquid present on or in a heat exchanger module (2, 2.1, 2.2) is/are taken along by the airflow.
 14. A method in accordance with claim 13, characterized in that the quantity of the liquid (10, 10′, 10″) supplied for the purpose of wetting the microchannel heat transfer elements (6.1, 6.2) and/or the heat exchange ribs (7, 7′, 7″, 7.1, 7.2) and the speed of the airflow (12, 12′, 12″) are regulated such that the gravity and/or the inertia forces which act on drops of the liquid on or in a heat exchanger module (2, 2.1, 2.2) are in balance with the buoyancy forces of the airflow. 